Cutting mill



Nov. 21, 1967 w. ZIMMERMANN CUTTING MILL Filed April 20, 1964 FIG. 1

INVENTOR. WALTER Z l MMER MANN BY MW YZWWM ATTORNEYS United States Patent Ofiice Patented Nov. 21", I967 3,353,755 CUTTING MILL Walter Zimmermanu, Goggingen, Germany, assignor to Alpine Aktiengeseilschaft; Augsburg, Germanyga conupanyof Germany Filed Apr. 20, 1964, Ser. No. 361,615 7 Claims. (Cl. 241--73) This invention concerns a cutting mill, particularly suited for cutting up plastic materials, specifically a mill construction in which the charge is introduced to the face of the rotor. In this construction a knife-carrying rotor works against knives fastened in the housing wall of the mill, with a charge-feeding channel above it. The invention concerns a special arrangement of the cutting chamber and of the feeding channel which permits cutting of parts which are large in comparison to the size of the rotor.

In known cutting mills having obliquely or vertically arranged rotor axes, the. parts to be reduced or cut-up are pulled toward the cutting edges either by rotor parts extending into the feeding channel, in collaboration with par-ts of the channel, or by helical guide rails, along which the material is pushed to the stator knives by rotor arms or upper cutting" edges of the knives. In both cases, the reduction" in cross section of the channel and hence the maximum size of the individual pieces of the charge causedby these elements constitutes a disadvantage. Let us consider particularly the arrangement with guide rails which has largely'displaced the other type of construction mentioned above.

According to the conception hitherto prevalent, the circle described by the cutting edges of the rotor knives corresponds to the maximum usable channel cross section; Now, practical application required a certain size for the space covered by the guide rails so that particularly hollow bodies without special corners and attack surfaces could also be gripped. Since the channel must not be narrowed toward the rotor so that parts of the charge cannot settle or wedge in, the size of the channel is thereby considerably reduced.

Another disadvantage'turned out to be that the last pieces of a certain'type of charge'danced on top of the rotor until they were caught, if no column of charge in the channel'pres'sedthe'lowest piece of the charge onto the rotor. It may be assumed that the cause for this is the relatively highcircumferential speed'of the rotor of about 10 m./sec., which is necessary for cutting, does not leave these pieces sufficient time to fall into the recesses of the rotor by their own weight, particularly into the respective space before the rotor knives, in order to be pulled in. In many cases, these pieces are pushed back into the feeding channel.

The foregoing disadvantages are eliminated by the present invention. According to the invention the cylindricalfigure defined in space by the knives of the rotor during rotation is no longer enclosedover its entire circumference, as heretofore, by a closed chamber with sieve and stator knives leaving a gap of only a few millimeters, rather'the rotor is located'eccentrically in a considerably larger cutting chamber enclosing it. While this reduces somewhat the size of the sieve surface possible and the number of stator knives to'be accommodated, it permits considerable enlargement of the feed channel cross section, with the rotor diameter remaining the same.

Now, with the new construction, the charge is no longer pulled in by supporting itself against guide rails, but preferably in the rotor plane before the first stator knife in the aperture, which narrows in wedge-like fashion, between the knife circle of the rotor and the wall of the cutting chamber, where the charge is caught and pulled in. Besides the considerable enlargement of the channel, the invention offers the advantage that voluminous, bulky or hard-to-catch pieces can fall into the part of the cut ting chamber which is not scanned by the rotor, is very quickly caught and not pushed back into the channel as much as in prior mills.

The cutting chamber is made essentially circular, or elliptical so that a pregranulated charge, tossed into the cutting chamber enlargement by the rotor arms, can proceed rapidly along the round wall of the cutting chambet and immediately, with as little retardation as possible, is reintroduced into the narrowing part for further cutting. Also, larger pieccs of the charge canrotate more easily, thus making it possible to introduce such pieces, with any pronounced protrusions which they might have, to the drawing-in point. In view of the motion of the charge and in the interest of accommodating as much sieving surface and as many stator knives as possible, it may'und'er certain circumstances be better not to have the rotor circle contact the possibly round cutting chamber, but to have the two circles overlap, thus generating a unilateral recess for the rotor.

The circular cutting chamber can be cylindrically extended upward as a feeding channel for the charge, therer by, if necessary, the mentioned recess for the rotor, in

which the stator knives and a sieve can be arranged, is covered so that the charge traversing the sieve there, cannot escape upwards.

This cover for the recess can advantageously be made as a helical guide rail to further improve the manner in which the charge is pulled'in.

Theaxis of the feed channel and rotor is advantageously arranged obliquely, preferably at an angle of from 30 to 60 to horizontal, so that the charge slides toward the rotor by its own weight from the channel as well as from that part of the bottom of the cutting chamber which is not scanned by the rotor.

In order to'prevent pieces of the charge from supporting themselves on the face of the rotor and'to bring the piece as quickly as possible into a good'drawing-in position at the drawing-in wedge, teeth or the like may be arranged'on the end face of the rotor in a manner known as such.

The accompanying drawing illustrates schematically one embodiment or example of the invention.

In the drawing:

FIG. 1 is a view ofa cutting mill according to the invention, partly in section taken along the line 1-1 of FIG. 3;

FIG. 2 is a view through the cutting chamber taken' looking into'the feed channelandshowingthe attachment face of the'feed channel structure.

The material to be cut is filled into a channel 3 from a feeding chute 1 through protective curtain 2' and falls into the area of a rotor 4. The rotor 4- is provided with knives 4' and is located eccentrically in the farlarger cutting chamber 6. The space 5 scanned by the rotor and the cutting chamber 6 intersect at the locations of two spaced stator knives 7 so'that, as seen in the rotational direction of the rotor 4 in FIG. 2, a gap 8, narrowing in wedge-like fashion, is formed as well as the unilateral recess 9. This recess 9 is limited by the stator knives 7 and bounded on the bottom partly by a sieve 10 which permits sufiiciently reduced material to escape into and be discharged through an exit chute or duct 11. The pieces of the charge in the channel 3 either fall directly into the part of cutting chamber 6 which is not scanned by rotor 4, or first onto rotor 4 which turns them and, under circumstances, tosses them off tangentially so that in both e9 cases the pieces are driven through and in front of gap 8, pulled in by the rotor knives and reduced before the upper stator knife 7 in FIG. 2.

This process is favored by the essentially cylindrical shape of the cutting chamber 6, the eccentrically located rotor therein in which the charge is quickly introduced to the catching gap, and by the oblique arrangement of the feed channel and the cutting chamber at an angle from about 30 to 60 off horizontal. On account of this arrangement, the charge can slide by its own weight in channel 3 as well as to the portion of the bottom of cutting chamber 6 not scanned by the rotor, and into the catching range of the rotor. The circular cutting chamber 6 is cylindrical and extends obliquely upwards, and as shown in FIGS. 2 and 3 the feeder channel 3 constitutes a cylindrical extension of the cutting chamber 6.

The unilateral recess 9 is covered at its upper end by a helical guide rail or wall 12 to further improve the catching ability of the rotor. Teeth 13 are attached to the upper face of rotor 4 to move pieces of the charge toward the cutting gaps and prevent them from being sup ported on the face of the rotor. The teeth 13 may be pointed knife-like projections as indicated on the face of the rotor 4, as shown in FIGS. 1 and 2. The stationary or bed knives 7 may be mounted in the manner indicated in FIG. 2, while the sieve is shown to be held in position by means of brackets 14 and studs 15. The mesh of the sieve may vary between 1 and mm., preferably between 4 and 8 mm., according to the size desired for the cut-up material. The curtain 2 is provided to prevent pieces of material from being thrown back out of the channel 3 and to reduce the sound from the cutting operation. It may be made of rubber, plastic material or chains and pivotally mounted at the top of the channel 3 so that it can swing to the right as material is fed against it. The rotor 4- is mounted on a drive shaft 16 extending through suitable mounting bearings in the end wall of the cutting chamber 6. The shaft 16 and rotor may be driven by a suitable electric motor or other means not shown.

The cutting mill according to the invention is particularly useful for cutting up scrap plastic materials for particular purposes or for remelting and reuse. The mill, of course, can be used for reducing the size of other materials to a desired value, for intsance leather or rubber. The pieces of material fed into the mill may be pre-reduced to a reasonable size and the mill has the advantage that the feeding channel 3 can be supplied or filled over its whole cross-sectional area with pieces of various shape and size.

I claim:

1. In a cutting mill for reducing the size of parts of material, particularly hollow bodies made of plastic or any other tough material, including a cylindrically shaped cutting chamber provided with spaced stator knives firmly mounted at the periphery thereof, a rotor fitted in the cutting chamber and equipped with cutting knives having cutting edges parallel to the axis of rotation of the rotor and cooperating with the stator knives, and a feeding funnel connected with the cutting chamber so as to feed the parts of material to be comminuted to the top face of said rotor, wherein the improvement comprises a cutting chamber having a diameter significantly larger than the diameter of the rotor for enabling the cutting-up of hollow bodies large-sized in relation to the rotor, the cutting chamber being provided with a recess in which the rotor is positioned, the rotor being located in such an eccentric position in the cutting chamber that, while the rotor is revolving, the outer edges of the knives fitted to said rotor, come into close relation to the interior wall of the cutting chamber said stator knives mounted in the cutting chamber extending in the direction of the rotor axis, one being provided on each side of the recess, and an outwardly bent sieve sheet located inside the recess between the two stator knives and arranged in concentric position with respect to the rotor.

2. A cutting mill according to claim 1, wherein the recess comprises a concavity of the cutting chamber partly sheltering the rotor and provided with a covering on the topside.

3. A cutting mill according to claim 2, wherein the covering of the concavity is helically shaped and arranged at an incline, in the direction of rotation of the rotor with respect to the top face of said rotor.

4. A cutting mill according to claim 3, wherein the cutting chamber is closed at its lower end and mounted at an incline with respect to the horizontal.

5. A cutting mill according to claim 1, wherein the cutting chamber and the axis of the rotor are mounted at an oblique angle of from 30 to with respect to the horizontal, and wherein the feeding channel extends upwardly from the cutting chamber at substantially the same angle.

6. In a cutting mill for reducing the size of parts of material, particularly hollow bodies made of plastic or any other tough material, including a cylindrically shaped cutting chamber provided with spaced stator knives firmly mounted at the periphery thereof, a rotor fitted in the cutting chamber and equipped with cutting knives having cutting edges parallel to the axis of rotation of the rotor and cooperating with the stator knives, and a feeding funnel connected with the cutting chamber so as to feed the parts of material to be comminuted to the top face of said rotor, wherein the improvement comprises a cutting chamber mounted with its axis extending at an incline with respect to the horizontal, is closed at its lower end and said rotor is mounted in said chamber with its axis parallel to the axis of the chamber and defines a scanning space intersecting the cylindrical figure of the cutting chamber at two points both of which are located to one side of a plane extending through the axis of the cutting chamber, said cutting chamber having a diameter significantly larger than the diameter of the rotor for enabiing the cutting-up of hollow bodies large-sized in relation to the rotor, and wherein the rotor is located in such an eccentric position in the cutting chamber that, while the rotor is revolving, the outer edges of the knives fitted to said rotor, come into close relation to the interior wall of the cutting chamber.

7. A cutting mill according to claim 6, wherein the cutting chamber and the axis of the rotor are mounted at an oblique angle of from 30 to 60 with respect to the horizontal, and wherein the feeding channel extends upwardly from the cutting chamber at substantially the same angle.

References Cited UNITED STATES PATENTS 1,133,181 3/1915 Philipp 241 X 1,672,544 6/1928 Tynders 241-221 X 2,066,621 1/1937 Gray 241189 2,583,997 1/1952 Chester 241-277 X 2,947,486 8/1960 Higer 24l-46.1 X

ROBERT C. RIORDON, Primary Examiner.

D. KELLY, Assistant Examiner. 

1. IN A CUTTING MILL FOR REDUCING THE SIZE OF PARTS OF MATERIAL, PARTICULARLY HOLLOW BODIES MADE OF PLASTIC OR ANY OTHER TOUGH MATERIAL, INCLUDING A CYLINDRICALLY SHAPED CUTTING CHAMBER PROVIDED WITH SPACED STATOR KNIVES FIRMLY MOUNTED AT THE PERIPHERY THEREOF, A ROTOR FITTED IN THE CUTTING CHAMBER AND EQUIPPED WITH CUTTING KNIVES HAVING CUTTING EDGES PARALLEL TO THE AXIS OF ROTATION OF THE ROTOR AND COOPERATING WITH THE STATOR KNIVES, AND A FEEDING FUNNEL CONNECTED WITH THE CUTTING CHAMBER SO AS TO FEED THE PARTS OF MATERIAL TO BE COMMINUTED TO THE TOP FACE OF SAID ROTOR, WHEREIN THE IMPROVEMENT COMPRISES A CUTTING CHAMBER HAVING A DIAMETER SIGNIFICANTLY LARGER THAN THE DIAMETER OF THE ROTOR FOR ENABLING THE CUTTING-UP OF HOLLOW BODIES LARGE-SIZED IN RELATION TO THE ROTOR, THE CUTTING CHAMBER BEING PROVIDED WITH A RECESS IN WHICH THE ROTOR IS POSITIONED, THE ROTOR BEING LOCATED IN SUCH AN ECCENTRIC POSITION IN THE CUTTING CHAMBER THAT, WHILE THE ROTOR IS REVOLVING, THE OUTER EDGES OF THE KNIVES FITTED TO SAID ROTOR, COME INTO CLOSE RELATION TO THE INTERIOR WALL 